Kinetics and mechanism of aminolysis of aryl cyclobutanecarboxylates in acetonitrile

Abstract

The aminolysis of Z-aryl cyclobutanecarboxylates (II) with X-benzylamines is investigated in acetonitrile at 55.0 °C. The rates are uniformly greater by 2.2 times than the corresponding rates of aryl cyclopropanecarboxylates (III). All the selectivity parameters, ρ_X (β_X), ρ_Z (β_Z) and ρ_XZ, are quite similar for the two substrates II and III. The k_H/k_D values involving deuterated benzylamines (XC₆H₄CH₂ND₂) are greater than unity, but are marginally smaller than those for the reactions of III. Low ΔH^‡ and large negative ΔS^‡ values are obtained and adherence to the reactivity–selectivity principle is observed. All these results are consistent with a stepwise mechanism with rate-limiting expulsion of a leaving group (aryl oxides) from a tetrahedral intermediate, T^±, with a hydrogen-bonded, four-center transition state.